This invention relates to an apparatus of the type used to subject culture media and/or instruments to low temperatures below 100.degree. Centigrade for predetermined time periods; also referred to as low temperature sterilization.
One method in the prior art for providing low temperature sterilization is described in U.S. Pat. No. 4,395,383. Such prior art device wastes large amounts of energy in the form of condensed steam which is continuously passed to drain. Additionally, this device requires numerous control in the sensing mechanism in order to get the chamber to its working temperature and maintain the chamber at such temperature.
Co-pending patent application, serial no. 901,230, filed Aug. 28, 1986 and continuation-in-part filed thereafter (which is currently owned by the assignee of this application) discloses an apparatus and method for low temperature sterilization wherein steam is introduced into a sterilization chamber in response to a temperature being sensed. In one aspect of the invention steam is introduced into the chamber until reaching a preselected temperature. A vacuum is applied to the chamber to lower the pressure in the chamber until reaching a second preset temperature. Steam is allowed to reenter the chamber to raise the temperature to the preselected temperature. This sequence is repeated until the temperature is stabilized and the exposure phase begins. This method is relatively slow in bringing the temperature of the chamber to the preselected exposure temperature and sometimes inconsistant if a previous cycle had recently been completed. A variation of this method was to pull a deep vacuum and then let the alternating steam and vacuum raise the pressure to the preselected operating temperature. This method was consistent but very slow, especially for temperatures above 90.degree. wherein a slight vacuum was required.
Applicant has invented a new method and apparatus wherein the conditioning phase of the sterilization cycle is both fast and consistent.